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US steel trade war



 
 
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  #41  
Old March 12th 18, 03:59 AM posted to rec.bicycles.tech
Emanuel Berg[_2_]
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Posts: 1,035
Default US steel trade war

John B. wrote:

One of the problems is that simply welding or
brazing two or more pieces together will
normally result in some distortion.


If it is not a problem, care to elaborate how
and when in the process this happens?

--
underground experts united
http://user.it.uu.se/~embe8573
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  #42  
Old March 12th 18, 06:30 AM posted to rec.bicycles.tech
John B.[_3_]
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Posts: 5,697
Default US steel trade war

On Mon, 12 Mar 2018 03:59:18 +0100, Emanuel Berg
wrote:

John B. wrote:

One of the problems is that simply welding or
brazing two or more pieces together will
normally result in some distortion.


If it is not a problem, care to elaborate how
and when in the process this happens?


Sure. When you heat, or melt a metal it expands. If you bond two
pieces of metal when they are hot, or molten, i.e. in it's expanded
state when it cools and shrinks there has to distortion or if the
parts are not free to move extreme stress will be imposed. See:
https://tinyurl.com/y7feu33f

This effect is even used to fasten two parts together - a shrink fit.

This isn't esoteric information. Every engineer understands it, every
welder understands it. You can even see the effect if you have over
head high voltage electrical transmission lines, the "sag" of the
wires is more on hot days then in freezing weather.
--
Cheers,

John B.

  #43  
Old March 12th 18, 06:55 AM posted to rec.bicycles.tech
John B.[_3_]
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Posts: 5,697
Default US steel trade war

On Mon, 12 Mar 2018 12:30:04 +0700, John B.
wrote:

On Mon, 12 Mar 2018 03:59:18 +0100, Emanuel Berg
wrote:

John B. wrote:

One of the problems is that simply welding or
brazing two or more pieces together will
normally result in some distortion.


If it is not a problem, care to elaborate how
and when in the process this happens?


Addition to below.

"If it is not a problem"? Quite the contrary, it is a problem that
occurs in any structure that is exposed to temperature variation.

Sure. When you heat, or melt a metal it expands. If you bond two
pieces of metal when they are hot, or molten, i.e. in it's expanded
state when it cools and shrinks there has to distortion or if the
parts are not free to move extreme stress will be imposed. See:
https://tinyurl.com/y7feu33f

This effect is even used to fasten two parts together - a shrink fit.

This isn't esoteric information. Every engineer understands it, every
welder understands it. You can even see the effect if you have over
head high voltage electrical transmission lines, the "sag" of the
wires is more on hot days then in freezing weather.

--
Cheers,

John B.

  #44  
Old March 12th 18, 02:14 PM posted to rec.bicycles.tech
Emanuel Berg[_2_]
external usenet poster
 
Posts: 1,035
Default US steel trade war

John B. wrote:

Sure. When you heat, or melt a metal it
expands. If you bond two pieces of metal when
they are hot, or molten, i.e. in it's
expanded state when it cools and shrinks
there has to distortion or if the parts are
not free to move extreme stress will be
imposed. See: https://tinyurl.com/y7feu33f


Still, the area affected is local if we assume
two long tubes being put into one so what is
distorted is the intersection area (plus
change) and by implication the angle or
relative positions of the two tubes/tube parts?

--
underground experts united
http://user.it.uu.se/~embe8573
  #45  
Old March 12th 18, 02:40 PM posted to rec.bicycles.tech
AMuzi
external usenet poster
 
Posts: 13,447
Default US steel trade war

On 3/12/2018 8:14 AM, Emanuel Berg wrote:
John B. wrote:

Sure. When you heat, or melt a metal it
expands. If you bond two pieces of metal when
they are hot, or molten, i.e. in it's
expanded state when it cools and shrinks
there has to distortion or if the parts are
not free to move extreme stress will be
imposed. See: https://tinyurl.com/y7feu33f


Still, the area affected is local if we assume
two long tubes being put into one so what is
distorted is the intersection area (plus
change) and by implication the angle or
relative positions of the two tubes/tube parts?


In a closed figure, overall expansion/contraction is a real
problem.

brief review of expansion/warp in welded structures:
http://www.lincolnelectric.com/en-us...on-detail.aspx

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971


  #46  
Old March 12th 18, 04:17 PM posted to rec.bicycles.tech
Emanuel Berg[_2_]
external usenet poster
 
Posts: 1,035
Default US steel trade war

AMuzi wrote:

In a closed figure, overall
expansion/contraction is a real problem.


When you see guys do aluminium tubes with MIG
or TIG one gets the impression that the filler
metal and gas/weld area sure is warm enough but
for the whole structure to disalign from this
isn't something I instantly think of...

I suppose the bicycle frame fixtures have
clamps to allow just the right minimal play so
that tubes don't suffer too much stress/strain
while at the same time still remain in their
right places with enough stability?

--
underground experts united
http://user.it.uu.se/~embe8573
  #47  
Old March 12th 18, 04:27 PM posted to rec.bicycles.tech
Frank Krygowski[_4_]
external usenet poster
 
Posts: 10,538
Default US steel trade war

On 3/12/2018 9:14 AM, Emanuel Berg wrote:
John B. wrote:

Sure. When you heat, or melt a metal it
expands. If you bond two pieces of metal when
they are hot, or molten, i.e. in it's
expanded state when it cools and shrinks
there has to distortion or if the parts are
not free to move extreme stress will be
imposed. See: https://tinyurl.com/y7feu33f


Still, the area affected is local if we assume
two long tubes being put into one so what is
distorted is the intersection area (plus
change) and by implication the angle or
relative positions of the two tubes/tube parts?


The very first welding project I ever did was back in the 1970s. I
designed and built a little 4' wide, 6'long, 1' deep utility trailer to
tow behind our car. The frame is steel angle. Visualize a two horizontal
4' x 6' rectangles of welded steel, with the upper one resting above the
lower one on 1' tall vertical steel struts.

So after a couple preliminary welding lessons, I welded up the two 4x6
rectangles flat on the workshop floor, then clamped them and the
vertical struts together and, working late at night, hurried to weld the
verticals. I rushed through the job, then left for home.

When I returned the next day, I was very disappointed to see that the
trailer "box" was no longer nicely square. The distortion from welding
had sort of pulled a rear corner upward an inch or more.

I didn't try to correct it, because the trailer was a rush job, and it's
plenty strong. There's not much chance of dangerous residual stresses.
The trailer's done lots of heavy hauling, and I still use it
occasionally. But its not as pretty as I would have liked.

--
- Frank Krygowski
  #48  
Old March 12th 18, 04:36 PM posted to rec.bicycles.tech
Frank Krygowski[_4_]
external usenet poster
 
Posts: 10,538
Default US steel trade war

On 3/12/2018 1:30 AM, John B. wrote:
On Mon, 12 Mar 2018 03:59:18 +0100, Emanuel Berg
wrote:

John B. wrote:

One of the problems is that simply welding or
brazing two or more pieces together will
normally result in some distortion.


If it is not a problem, care to elaborate how
and when in the process this happens?


Sure. When you heat, or melt a metal it expands. If you bond two
pieces of metal when they are hot, or molten, i.e. in it's expanded
state when it cools and shrinks there has to distortion or if the
parts are not free to move extreme stress will be imposed. See:
https://tinyurl.com/y7feu33f

This effect is even used to fasten two parts together - a shrink fit.

This isn't esoteric information. Every engineer understands it, every
welder understands it. You can even see the effect if you have over
head high voltage electrical transmission lines, the "sag" of the
wires is more on hot days then in freezing weather.


One company I visited once also used the effect to remove distortion.
They made big weldments, like the long steel arm brush trimmers that
highway departments use to clear plants near roadsides.

Those arms are welded up of long steel plates, and usually came out of
the welds not very straight. They had guys with big torches who were
skilled at "flame straightening," i.e. heating the outside of a bend
just the right amount so when it cooled, it pulled the arm straight.

--
- Frank Krygowski
  #49  
Old March 12th 18, 05:05 PM posted to rec.bicycles.tech
John B.[_3_]
external usenet poster
 
Posts: 5,697
Default US steel trade war

On Mon, 12 Mar 2018 14:14:04 +0100, Emanuel Berg
wrote:

John B. wrote:

Sure. When you heat, or melt a metal it
expands. If you bond two pieces of metal when
they are hot, or molten, i.e. in it's
expanded state when it cools and shrinks
there has to distortion or if the parts are
not free to move extreme stress will be
imposed. See: https://tinyurl.com/y7feu33f


Still, the area affected is local if we assume
two long tubes being put into one so what is
distorted is the intersection area (plus
change) and by implication the angle or
relative positions of the two tubes/tube parts?


In building a bicycle frame one is essentially making two triangles
and distortion will have an effect.
--
Cheers,

John B.

  #50  
Old March 12th 18, 05:09 PM posted to rec.bicycles.tech
John B.[_3_]
external usenet poster
 
Posts: 5,697
Default US steel trade war

On Mon, 12 Mar 2018 14:14:04 +0100, Emanuel Berg
wrote:

John B. wrote:

Sure. When you heat, or melt a metal it
expands. If you bond two pieces of metal when
they are hot, or molten, i.e. in it's
expanded state when it cools and shrinks
there has to distortion or if the parts are
not free to move extreme stress will be
imposed. See: https://tinyurl.com/y7feu33f


Still, the area affected is local if we assume
two long tubes being put into one so what is
distorted is the intersection area (plus
change) and by implication the angle or
relative positions of the two tubes/tube parts?


Building a bicycle frame is essentially making two triangles and
distortion of any part of a triangle will have rather drastic effects
on the triangle.
--
Cheers,

John B.

 




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